1. Technical Field
This application relates to the art of thermostat mounting clips and, more particularly, to spring clips for attaching thermostats to tubing in heat exchange relationship therewith. The invention is particularly applicable for use with thermostats that have a bimetal disc within a thermostat cup and will be described with particular reference thereto. However, it will be appreciated that the invention has broader aspects and the spring clip can be used for other purposes as well as with other types of thermostats.
2. Discussion
In a known arrangement for attaching thermostats to tubing, a generally U-shaped spring clip is welded to the bottom wall of the thermostat cup. The generally U-shaped clip makes line contact with the thermostat cup bottom wall, and is positioned so that insertion forces during attachment of the clip to the tubing act perpendicular to the thermostat cup bottom wall. These forces tend to permanently deform the thermostat cup bottom wall and this may cause improper operation of the thermostat. In addition, accidental bumping of the clip or dropping the thermostat on the clip can permanently distort the thermostat cup bottom wall in a manner that interferes with proper thermostat operation.
A prior art thermostat and clip arrangement of the type described is illustrated in FIG. 7 where a generally cylindrical thermostat cup 2 has a generally U-shaped spring clip 3 welded to its flat bottom wall 4. Clip 3 makes little more than line contact with bottom wall 4 as generally indicated at 5. The spaced-apart end portions of the arms of clip 3 define an entrance opening 6 that is centered on thermostat longitudinal axis 7. Entrance opening 6 opens outwardly in a direction parallel to axis 7 and perpendicular to thermostat bottom wall 4. Therefore, installation of clip 3 on tubing results in forces being applied to thermostat cup bottom wall 4 in a direction perpendicular thereto. Because clip 3 is welded to bottom wall 4 along a small area, these forces are concentrated and may permanently deform bottom wall 4.
It would be desirable to have an arrangement that minimizes possible damage to the bottom wall of the thermostat cup during attachment of the thermostat to tubing and to otherwise minimize possible deformation of the bottom wall by forces applied thereto through the mounting clip. Additionally, it is well known that tubing manufactured for use in, for example, the refrigeration and HVAC industries is not subject to exacting tolerances for geometric dimensions, including roundness. Furthermore, it is often the case that thermostats, like the one disclosed here, are employed in situations where they are clipped to tubing that is not round, such as when the tubing is bent at an elbow or xe2x80x9ckinkedxe2x80x9d such that the cross-sectional configuration of the tubing is other than substantially circular. Consequently, the need has arisen for a thermostat spring clip that can attach to both tubing that exhibits a substantially circular cross-section and tubing that exhibits a non-circular or xe2x80x9cout-of-roundxe2x80x9d cross-section while still maintaining a low insertion force, high clamping force, and still maintaining good thermal response in the thermostat.
A substantially flat mounting base on a spring clip is attached to a substantially flat bottom wall of a thermostat disc cup. The substantially flat mounting base occupies a large amount of the bottom wall area to minimize the possibility of the bottom wall being deformed by forces applied to the clip.
In a preferred arrangement, the spring clip has an entrance opening that opens in a direction transversely of the longitudinal axis of the thermostat cup. Therefore, forces applied to the clip during the attachment of same to tubing act generally parallel to the bottom wall of the thermostat cup to further minimize the possibility of bottom wall deformation by installation forces.
The spring clip has a spring arm integral with the mounting base and is positioned so that the tubing is received between the mounting base and the spring arm. The spring arm has a tubing receiving portion therein to provide high resistance against displacement of the tubing from the spring clip. The tubing receiving portion may be curved on the radius of a circle that generally corresponds to the external curvature of tubing that is received within the spring clip. In an alternative arrangement, the tubing receiving portion comprises a generally abrupt arcuate portion extending through an angle of approximately 90xc2x0 and two adjacent non-arcuate portions adjoining either side of the arcuate portion. The resulting tubing receiving portion in conjunction with the mounting base contains the tubing securely at three points about the circumference of the tubing.
It is a principal object of the present invention to provide an improved spring clip for attaching a thermostat cup to tubing.
It is a further object of the invention to provide an improved thermostat clip that improves the thermal response of the thermostat and that is easier to weld to the bottom wall of a thermostat disc cup.
It is another object of the invention to provide an improved thermostat disc cup and spring clip assembly that facilitates attachment of the thermostat cup to tubing while providing high resistance to displacement of the thermostat disc cup from its attachment to tubing.
It is an additional object of the invention to provide an improved arrangement for attaching a spring clip to the bottom wall of a thermostat disc cup in a manner that minimizes the possibility that the bottom wall will be deformed by forces applied to the spring clip.
It is a further object of the invention to provide an improved thermostat disc cup and spring clip assembly that requires relatively low installation force while providing relatively high retention force.
It is yet another object of the present invention to provide an improved thermostat disc cup and spring clip assembly that can be used with tubing having both substantially circular and non-circular cross-sections.
Compared to the previous design of FIG. 7, the design of the present application requires an insertion force that is only approximately 29% of the insertion force of the previous design. At the same time, the design of the present application provides an average increase of approximately 10% in retention force compared to the previous design of FIG. 7. The large surface area of the mounting base of the clip and the large surface area of engagement between such base and the bottom wall of the thermostat disc cup provides a 22% improvement in thermal response compared to the design of FIG. 7. Compared to the design of FIG. 7, the design of this application provides about 60 times more dent resistance for the cup bottom wall in a 20 pound deformation test. For drop impact testing at a distance of six feet, the clip of the present application has about 24 times more dent resistance than the arrangement of FIG. 7.